408 



MANUAL OF ELEMENTARY ZOOLOGY 



second one. In the pelvic girdle there is a long ilium, 

 reaching a good way behind as well as in front of the 

 acetabulum, and connected with the sacrum along nearly 

 the whole of its inner side. This, together with the length 

 of the sacrum, enables the trunk to be supported by the 

 single pair of legs in a more or 

 less horizontal position. The 

 acetabulum is placed near 

 the middle of the ilium. The 

 ischium is a fiat, backwardly 

 directed bone. Its hinder part 

 is fused with the ilium, but just 

 after the acetabulum an oval 

 opening — the iliosciatic foramen 

 — lies between the two. The 

 pubis is slender and also directed 

 backwards. In many birds it 

 has a small prepubic process in 

 front. The obturator foramen 

 is slit-like. There is no sym- 

 physis or ventral junction of 

 the girdles. The hind-limb has 

 a short, stout femur, a long 

 tibia, a slender fibula, partly 

 joined to the tibia below, no 

 free tarsals, these bones being 

 fused to the tibia and meta- 

 tarsals, a single tarso-metatarsus 

 formed by the union of the 

 distal tarsals with the meta- 

 *., body of the tarsals (except the small, free, 

 first metatarsal), and four toes, 

 each of several joints. 



The most conspicuous part of 

 the muscular system is the great pectoral muscles. The 

 pectoralis major, arising from the sternum and 

 ftrfangements. clavicle, is inserted on the under side of the 

 humerus, which it pulls downwards, thus raising 

 the bird and driving it forward by the wing-beat in flight. 

 The smaller pectoralis minor arises from the sternum above 

 the major and passes through the foramen triosseum and 



Fig. 298. — The hyoid appar- 

 atus of a pigeon. 



a.c, Anterior cornu 



hyoid; b.br.i, b.br.2, basi 

 branchials ; b.hd. t basihyoid 

 /.£., posterior cornu. 



